Ethnobotanical, phytochemical and antiplasmodial studies of Neoboutonia Macrocalyx L

Abstract

Malaria is one of the leading causes of mortality and morbidity due to resistance of the parasite to the cheap and available antimalarials. The need for effective new and cheap alternative antimalarials is therefore of utmost importance. The study was done to document medicinal plants and determine the antiplasmodial activity, toxicity and chemical structures of the active compounds from extracts of one medicinal plant species. Different medicinal plants (131 species) distributed over 55 families were observed to be used by the local communities around the Northern sector of Kibale National Park. From the list of medicinal plants established in this study, Neoboutonia macrocalyx, a plant commonly used for treating malaria was selected for further research. The ethylacetate extract of the leaves and stem bark showed a 90% and 63% growth inhibition against Plasmodium falciparum respectively. The LD50 of the stem aqueous extract of N. macrocalyx in mice was found to be 3775.73 mg/kg indicating low acute toxicity of the extract. Phytochemical investigation on the leaves of Neoboutonia macrocalyx yielded nine new cycloartane triterpenes (1-9) and one new phenanthrene (10) along with known terpenoids (11 and 12), a steroid (13) and a phthalate ester (14). The stem bark yielded a new diterpenoid named neoboutomacroin (15), a phenanthrene (16)), a sterol (17) and two diterpenoids; simplexin (18) and montanin (19). Compounds 1-8, 11-12 and 15 showed good antiplasmodial activities with IC50 ≤ 5 μM. The identification of antiplasmodial compounds from this plant suggests that they may be vital in the medicinal properties of this plant and the new identified compounds could serve as “hit” to the development of new malaria drugs. There is need for sensitization of the local community and herbalists to start growing medicinal plants in their gardens and around homesteads to conserve them and prevent their extinction especially N. macrocalyx which is endowed with antimalarial properties.